Method for fabricating an electronic component

ABSTRACT

A carrier and a semiconductor chip are provided. A connection layer is applied to a first main face of the semiconductor chip. The connection layer includes a plurality of depressions. A filler is applied to the connection layer or to the carrier. The semiconductor chip is attached to the carrier so that the connection layer is disposed between the semiconductor chip and the carrier. The semiconductor chip is affixed to the carrier.

TECHNICAL FIELD

The present invention relates to a method for fabricating an electroniccomponent and to an electronic component.

BACKGROUND

In many electronic components a semiconductor chip has to be mountedonto a carrier, in particular an electrically conductive carrier like,for example, a leadframe. It is important that the connection betweenthe semiconductor chip and the carrier is of high reliability andexhibits high electrical and thermal conductivity. During and after themounting process of the semiconductor chip onto the carrier, however,problems may occur depending on the applied fixation technology. Theproblems may arise, for example, from different thermal expansioncoefficients of the semiconductor material and the carrier materialwhich may lead to thermal mechanical stress. In case of thinnedsemiconductor chips these stress reactions may even lead to microscopicdamage of the semiconductor chip like the formation of cracks. In othercases the stress may lead to a strong deformation of the semiconductorsubstrate so that the following process steps are no long possible like,for example, laser drilling, lamination, wire bonding, etc. In generalthe stress generated in the semiconductor chip severely affects thereliability of the following process steps. Therefore, there is a needfor an interconnection technology which is able to provide a stable andpermanently reliable connection between a semiconductor chip and acarrier with high electrical and thermal conductivity.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of embodiments and are incorporated in and constitute apart of this specification. The drawings illustrate embodiments andtogether with the description serve to explain principles ofembodiments. Other embodiments and many of the intended advantages ofembodiments will be readily appreciated as they become better understoodby reference to the following detailed description. The elements of thedrawings are not necessarily to scale relative to each other. Likereference numerals designate corresponding similar parts.

FIG. 1 shows a flow diagram of a method for fabricating an electroniccomponent according to an embodiment;

FIGS. 2A and 2B, collectively FIG. 2, show a schematic cross-sectionalside view representation (FIG. 2A) and a down view representation (FIG.2B) of a semiconductor chip with contact pillars to illustrate a methodfor fabricating an electronic component according to an embodiment;

FIG. 3 shows a schematic cross-sectional side view representation of theassembly of FIG. 2 after filling a filler material into the intermediatespaces between the contact pillars;

FIG. 4 shows a schematic cross-sectional side view representation of anelectronic component obtained after attaching the assembly of FIG. 3onto a leadframe;

FIG. 5 shows a schematic cross-sectional side view representation of anelectronic component according to an embodiment; and

FIG. 6 shows a schematic cross-sectional side view representation of anelectronic component according to an embodiment.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The aspects and embodiments are now described with reference to thedrawings, wherein like reference numerals are generally utilized torefer to like elements throughout. In the following description, forpurposes of explanation, numerous specific details are set forth inorder to provide a thorough understanding of one or more aspects of theembodiments. It may be evident, however, to one skilled in the art thatone or more aspects of the embodiments may be practiced with a lesserdegree of the specific details. In other instances, known structures andelements are shown in schematic form in order to facilitate describingone or more aspects of the embodiments. It is to be understood thatother embodiments may be utilized and structural or logical changes maybe made without departing from the scope of the present invention. Itshould be noted further that the drawings are not to scale or notnecessarily to scale.

In addition, while a particular feature or aspect of an embodiment maybe disclosed with respect to only one of several implementations, suchfeature or aspect may be combined with one or more other features oraspects of the other implementations as may be desired and advantageousfor any given or particular application. Furthermore, to the extent thatthe terms “include,” “have,” “with” or other variants thereof are usedin either the detailed description or the claims, such terms areintended to be inclusive in a manner similar to the term “comprise.” Theterms “coupled” and “connected,” along with derivatives may be used. Itshould be understood that these terms may be used to indicate that twoelements cooperate or interact with each other regardless whether theyare in direct physical or electrical contact, or they are not in directcontact with each other. Also, the term “exemplary” is merely meant asan example, rather than the best or optimal. The following detaileddescription, therefore, is not to be taken in a limiting sense, and thescope of the present invention is defined by the appended claims.

The embodiments of an electronic component and a method for fabricatingan electronic component may use various types of semiconductor chips orcircuits incorporated in the semiconductor chips, among them logicintegrated circuits, analogue integrated circuits, mixed signalintegrated circuits, sensor circuits, MEMS(Micro-Electro-Mechanical-Systems), power integrated circuits, chipswith integrated passives, etc. The embodiments may also usesemiconductor chips comprising MOS transistor structures or verticaltransistor structures like, for example, IGBT (Insulated Gate BipolarTransistor) structures or, in general, transistor or other structures ordevices in which at least one electrical contact pad is arranged on afirst main face of the semiconductor chip and at least one otherelectrical contact pad is arranged on a second main face of thesemiconductor chip opposite to the first main face of the semiconductorchip.

In several embodiments layers or layer stacks are applied to one anotheror materials are applied or deposited onto layers. It should beappreciated that any such terms as “applied” or “deposited” are meant tocover literally all kinds and techniques of applying layers onto eachother. In particular, they are meant to cover techniques in which layersare applied at once as a whole like, for example, laminating techniquesas well as techniques in which layers are deposited in a sequentialmanner like, for example, sputtering, plating, molding, CVD, etc.

The semiconductor chips may comprise contact elements or contact pads onone or more of their outer surfaces wherein the contact elements servefor electrically contacting the semiconductor chips. The contactelements may have any desired form or shape. They can, for example, havethe form of lands, i.e., flat contact layers on an outer surface of thesemiconductor chip. The contact elements or contact pads may be madefrom any electrically conducting material, e.g., from a metal asaluminum, gold, or copper, for example, or a metal alloy, or anelectrically conducting organic material, or an electrically conductingsemiconductor material.

In the claims and in the following description different embodiments ofa method for fabricating an electronic component are described as aparticular sequence of processes or measures, in particular in the flowdiagram. It is to be noted that the embodiments should not be limited tothe particular sequence described. Particular ones or all of differentprocesses or measures can also be conducted simultaneously or in anyother useful and appropriate sequence.

Referring to FIG. 1, a flow diagram of a method for fabricating anelectronic module is shown. The method 100 of FIG. 1 comprises providinga carrier (110), providing a semiconductor chip (120), applying aconnection layer to a first main face of the semiconductor chip, theconnection layer comprising a plurality of depressions (130), applying afiller material to the connection layer or to the carrier (140),attaching the semiconductor chip with the connection layer to thecarrier (150), and applying one or more of heat, pressure andultra-sonic to fix the semiconductor chip to the carrier (160).

The filler material can either be filled directly into the depressionsof the connection layer or it can be applied onto the connection layerabove the pillars defining the depressions between them or it can beapplied to the carrier. Due to the subsequent treatment, the fillermaterial may flow into the depressions so that the depressions may becompletely filled with the filler material.

According to an embodiment of the method 100 of FIG. 1, the carrier iscomprised of an electrically conductive material. In particular, thecarrier can be comprised of a leadframe or any other metallic carrier.The carrier can also be comprised of an insulating material havingmetallized areas on a main face thereof or of a printed circuit board(PCB) or any other substrate.

According to an embodiment of the method 100 of FIG. 1, thesemiconductor chip comprises a first main face and a second main faceopposite to the first main face, wherein at least one electrical contactpad is arranged on the first main face and at least one electricalcontact pad is arranged on the second main face. According to anembodiment thereof, the semiconductor chip comprises a verticaltransistor structure like, for example, an IGBT (Insulated Gate BipolarTransistor) structure.

According to an embodiment of the method 100 of FIG. 1, thesemiconductor chip may comprise any kind of electrical device orelectrical circuit incorporated in the semiconductor chip, in particularone or more of a logic integrated circuit, an analog integrated circuit,a mixed signal integrated circuit, a sensor circuit, a MEMS(Micro-Electro-Mechanical-Systems), a power integrated circuit, atransistor like, for example, an MOS transistor, a power transistor, anIGBT transistor, or a vertical transistor.

According to an embodiment of the method 100 of FIG. 1, the depressionsof the connection layer can have any desired form and shape. Inparticular, the depressions can have equal form and shape or they can bedifferent in form and shape wherein also a part of the plurality ofdepressions can be equal in form and shape. The depressions or part ofthem can have a depth so that they reach through the layer until thefirst main face of the semiconductor chip, or the depressions or part ofthem can have a depth so that they do not reach through the layer untilthe first main face of the semiconductor chip. The depressions or partof them can have vertical side walls. The depressions can have arectangular-shaped cross-section. The topology of the pillars can alsobe adjusted to the topology of the carrier, e.g., the bump tips maydefine at least a plane for a planar carrier.

According to an embodiment of the method 100 of FIG. 1, the depressionscan be defined by pillars of the connection layer wherein thedepressions are comprised of intermediate spaces between the pillars.The pillars can have a lateral size in a range from 5 μm-50 μm and aheight in a range from 10 μm-30 μm, for example. The distances betweenthe pillars can be in a range from 5 μm-50 μm. The size of the pillarsand the distances between the pillars can be chosen such that thedepressions formed by the intermediate spaces between the pillars arecontiguous or non-contiguous. According to one example, the pillars andthe intermediate spaces between them are formed to a regular pattern, inparticular to a checkered pattern, in which case the pillars and theintermediate spaces between them occupy identical space volumes or, incase of very many pillars or big area pillars, the pillars may occupyonly a fraction of the total area with increased pitch between thepillars.

According to an embodiment of the method 100 of FIG. 1, the connectionlayer may be generated by applying a connection base layer to the mainface of the semiconductor chip and then removing predetermined portionsof the connection base layer. The predetermined portions of theconnection base layer can be removed by laser structuring or by etching.

According to an embodiment of the method 100 of FIG. 1, the connectionbase layer can be comprised of an electrically conductive material like,for example, copper or any other metallic material.

According to an embodiment of the method 100 of FIG. 1, the connectionbase layer can be comprised of an insulating material.

According to an embodiment of the method 100 of FIG. 1, the connectionlayer comprising the plurality of depressions can be fabricated by aphotolithographic method or a lift-off method.

According to an embodiment of the method 100 of FIG. 1, the fillermaterial is comprised of one or more of a heat-shrinkable material, anelectrically conductive material, an insulator material, a polymermaterial, an adhesive material, and anyone of the above-mentionedmaterials as a host material filled with particles, in particular one ormore of electrically conductive particles, insulating particles, andmicroscopic or nanoscopic particles.

According to an embodiment of the method 100 of FIG. 1, thesemiconductor chip is comprised of a semiconductor chip region of asemiconductor wafer, the semiconductor wafer comprising multiplesemiconductor chip regions. The multiple semiconductor chip regions maycomprise a common first main face. The connection layer may be appliedon a wafer level basis and, in particular, also the filling of thefiller material into the depressions may be performed on a wafer levelbasis. Thereafter, the semiconductor wafer may be separated intoindividual semiconductor chips. One of the semiconductor chips may thenbe attached to a carrier and fixed to it as described before.

Referring to FIGS. 2 to 4, there are shown schematic representations forillustrating a method for fabricating an electronic component. FIGS. 2Aand 2B show a schematic cross-sectional representation (A) and a downview representation (B) of a semiconductor chip 200 and a connectionlayer 250 applied to the semiconductor chip 200. FIG. 2A is across-section along line A-A of FIG. 2B. The semiconductor chip 200 canbe comprised of, for example, a silicon chip and can be furthercomprised of a chip having a first contact layer 210 disposed on a firstmain face of the semiconductor chip 200 and second and third contactlayers 220 and 230 disposed on a second main face opposite to the firstmain face. The semiconductor chip 200 can, for example, be comprised ofa vertical transistor chip like, for example, an IGBT (Insulated GateBipolar Transistor). The first, second and third contact layers 210, 220and 230 can be the drain, source and gate contact layers of an IGBT. Thesemiconductor chip 200 can have a thickness in a range from 50 μm-800μm, in particular from 50 μm-300 μm, in particular from 50 μm-100 μm.The semiconductor chip 200 can either be an individual semiconductorchip or a semiconductor chip region within a semiconductor wafer.

The connection layer 250 can be comprised of a regular array of contactpillars 251 and intermediate spaces (depressions) 252 between thecontact pillars 251. As shown in FIG. 2B, the arrangement of contactpillars 251 and intermediate spaces 252 can be that of a checker boardpattern which means that the total number of contact pillars 251 and thetotal number of intermediate spaces 252 occupy identical space volumes.In the embodiment shown in FIG. 2B, the intermediate spaces 252 areseparated from each other. However, it can also be the case that thecontact pillars 251 have smaller lateral dimensions or greater distancesbetween each other so that the intermediate spaces 252 between thecontact pillars 251 are connected with each other and form a contiguousempty space between die contact pillars 251. The contact pillars 251 canhave a rectangular cross-section and vertical side walls and theintermediate spaces 252 can also have rectangular cross-sections andvertical side walls. The pillars 251 can also have any other desiredshapes, e.g., Y-, U-, I-, or X-like shapes, and also non-verticalsidewalls, preferably those with an angle of over 90° versus the plane.The contact pillars 251 can have a width, i.e., a lateral edge length ina range from 5 μm-50 μm and a height in a range from 5 μm-30 μm. Thecontact pillars 251 can be made of a metallic material like, forexample, copper. They can be fabricated by depositing a copper layer andthereafter removing predetermined portions by, for example,photolithographic technology and etching. The predetermined portions areintended to become the intermediate spaces 252. As an alternative it isalso possible to deposit the copper layer through a mask, wherein themasking portions of the mask define areas where no copper is to bedeposited, i.e., regions corresponding to the intermediate spaces 252.

Referring to FIG. 3, there is shown a schematic cross-sectionalrepresentation of the assembly as shown in FIG. 2A after depositing afiller material 300 into the intermediate spaces 252. The fillermaterial 300 can be one or more of a heat-shrinkable material, anelectrically conductive material, an insulator material, an adhesivematerial, a polymer material, a non-conductive paste (NCP), anon-conductive foil, and any kind of host material filled withparticles, in particular conductive particles or insulating particles,in particular microscopic or nanoscopic particles. The filler materialcan, in particular, be comprised of an intrinsically conductive polymerlike, for example, doped or undoped polythiophen(Poly-(3,4-ethylendioxythiopen), which can be filled with electricallyconductive or insulating particles. The filler material 300 can bedeposited by different methods and technologies depending on the kindand nature of the filler material 300. The filler material 300 can, forexample, be filled into or over the intermediate spaces 252 byspin-coating, lamination, printing, or coating by means of a doctorblade or a squeegee.

Referring to FIG. 4, there is shown a cross-sectional representation ofthe assembly of FIG. 3 after attaching it to a carrier 400 like, forexample, a leadframe. The leadframe 400 can, for example, be made ofcopper or a copper alloy. The leadframe 400 may comprise a first, uppersurface 410 and a second, lower surface 420 opposite to the uppersurface 410. The leadframe 400 can have a silver or nickel plating of athickness in a range from 500 nm-5 μm at an entire surface thereof oronly on the first surface 410 where electrical devices are to beconnected.

The assembly shown in FIG. 3 comprising the semiconductor chip 200, theconnection layer 250 and the filling material 300 is attached to thefirst surface 410 of the leadframe 400. Then one or more of pressure,heat, and ultra-sound can be applied in order to fix the semiconductorchip to the leadframe 400 so that at first only a form-fit connectionbetween the semiconductor chip 200, the connection layer 250, thefilling material 300 and the leadframe 400 is established. Pressure canbe exerted from above and below to press the semiconductor chip 200 andthe leadframe 400 together and a temperature in a range from 100°C.-250° C., or 150° C. to 200° C., can be applied for 1-10 min to fixthe lower surface of the connection layer 250 and the filling material300 to the upper surface of the leadframe 400. As an alternative to theheat treating or in addition thereto, ultra-sonic radiation can bedirected to the junction between the semiconductor chip 200 and theleadframe 400.

A result of such a treatment, as described above, will be that anadhesive bond is developed between the filler material 300 and thecontact pillars 251, between the filler material 300 and the leadframe400, and between the contact pillars 251 and the leadframe 400. Theheat-shrinkability of the filler material 300 can be irreversible bynature of the filler material so that the adhesive bond between thesecomponents will be stable and permanently reliable. In operation of theelectrical device of the semiconductor chip, in particular a verticaltransistor, the adhesive bond can be even further enhanced due to theapplied voltage and the current flowing through the contacts due toelectro-diffusion and electro-migration and the resulting diffusion ofatoms from one side of anyone of the contact junctions to the otherside. Furthermore, the filler material 300 may act as a barrier formechanically induced cracks or tears which may occur in the connectionlayer, i.e., the contact pillars 251. As a result, there is not only anadvantage as regards the stability of the connection as also withrespect to electromigration issues that arise from solder basedcontacting.

Referring to FIG. 5, there is shown a schematic cross-sectional sideview representation of an electronic component according to anembodiment. The electronic component 500 comprises a carrier 510, asemiconductor chip 520 comprising a main face 521 and a first contactlayer 522 at the back surface, a connection layer 530 applied to themain face 521 of the semiconductor chip 520, the connection layer 530comprising a plurality of depressions 531, a filler material 540disposed within the depressions 531, wherein the connection layer 530 isdisposed between the semiconductor chip 520 and the carrier 510.

The electronic component can have any further feature as described abovein connection with the fabrication method. Only a few important featureswill be described in the following.

According to an embodiment of the electronic component 500 of FIG. 5,the carrier 510 is comprised of an electrically conductive material. Inparticular, the carrier 510 can be comprised of a leadframe or any othermetallic carrier. The carrier 510 can also be comprised of an insulatingmaterial having metallized areas on a main face thereof or of a printedcircuit board (PCB) or any other substrate.

According to an embodiment of the electronic component 500 of FIG. 5,the semiconductor chip 520 comprises a first main face and a second mainface opposite to the first main face, wherein at least one electricalcontact pad is arranged on the first main face and at least oneelectrical contact pad is arranged on the second main face. According toan embodiment thereof, the semiconductor chip 520 comprises a verticaltransistor structure like, for example, an IGBT (Insulated Gate BipolarTransistor) structure.

According to an embodiment of the electronic component 500 of FIG. 5,the semiconductor chip 520 may comprise any kind of electrical device orelectrical circuit incorporated in the semiconductor chip, among them alogic integrated circuit, an analog integrated circuit, a mixed signalintegrated circuit, a sensor circuit, a MEMS(Micro-Electro-Mechanical-Systems), a power integrated circuit, atransistor like, for example, an MOS transistor, an IGBT transistor, ora vertical transistor.

According to an embodiment of the electronic component 500 of FIG. 5,the depressions 531 of the connection layer 530 can have any desiredform and shape. In particular, the depressions 531 can have equal formand shape or they can be different in form and shape, wherein also apart of the plurality of depressions 531 can be equal in form and shape.The depressions 531 or part of them can have a depth so that they reachthrough the layer 530 until the first main face 521 of the semiconductorchip 520, or the depressions 531 or part of them can have a depth sothat they do not reach through the layer 530 until the first main face521 of the semiconductor chip 520. The depressions 531 or part of themcan have vertical side walls. The depressions 531 can have arectangular-shaped cross-section.

According to an embodiment of the electronic component 500 of FIG. 5,the depressions 531 can be defined by pillars 550 of the layer 530,wherein the depressions 531 are comprised of intermediate spaces betweenthe pillars 550. The pillars 550 can have a lateral size in a range from5 μm-50 μm and a height in a range from 10 μm-30 μm, for example. Thedistance between the pillars 550 can be in a range from 5 μm-500 μm ormore. The size of the pillars 550 and the distance between the pillars550 can be chosen such that the depressions 531 formed by theintermediate spaces between the pillars 550 are contiguous ornon-contiguous. According to one example, the pillars 550 and theintermediate spaces between them are formed to a regular pattern, inparticular to a checkered pattern, in which case the pillars 550 and theintermediate spaces between them occupy identical space volumes.According to an embodiment the area occupied by the pillars 550 is muchsmaller compared with the total area.

According to an embodiment of the electronic component 500 of FIG. 5,the connection layer 530 or the pillars 550 can be comprised of anelectrically conductive material like, for example, copper or any othermetallic material.

According to an embodiment of the electronic component 500 of FIG. 5,the connection layer 530 or the pillars 550 can be comprised of aninsulating material.

According to an embodiment of the electronic component 500 of FIG. 5,the connection layer 530 comprising the plurality of depressions can befabricated by a photolithographic method or a lift-off method.

According to an embodiment of the electronic component 500 of FIG. 5,the filler material 540 is comprised of one or more of a heat-shrinkablematerial, an electrically conductive material, an insulator material, apolymer material, an adhesive material, and anyone of theabove-mentioned materials as a host material filled with particles, inparticular one or more of electrically conductive particles, insulatingparticles and microscopic or nanoscopic particles.

Referring to FIG. 6, there is shown a schematic cross-sectional sideview representation of an electronic component according to anembodiment. The electronic component 600 of FIG. 6 is a furtherdevelopment of the electronic component 500 of FIG. 5. As far as thesame reference signs are used, the description of the respectiveelements will not be repeated here. The electronic component 600 inaddition comprises second and third contact layers 523 and 524 on afront surface of the semiconductor chip 520, wherein a furtherconnection layer 560 is applied to the contact layers 523 and 524. Theconnection layer 560 can be formed in the same way as the connectionlayer 530, namely by comprising depressions 570 defined by pillars 580.In a later stage connection elements may be connected to the connectionlayer 560 by use of a filler material in the same way as described abovefor the backside of the semiconductor chip.

While the invention has been illustrated and described with respect toone or more implementations, alterations and/or modifications may bemade to the illustrated examples without departing from the spirit andscope of the appended claims. In particular regard to the variousfunctions performed by the above described components or structures(assemblies, devices, circuits, systems, etc.), the terms (including areference to a “means”) used to describe such components are intended tocorrespond, unless otherwise indicated, to any component or structurewhich performs the specified function of the described component (e.g.,that is functionally equivalent), even though not structurallyequivalent to the disclosed structure which performs the function in theherein illustrated exemplary implementations of the invention.

What is claimed is:
 1. An electronic component, comprising: a carrier; asemiconductor chip comprising a main face; a connection layer disposedon the main face of the semiconductor chip, the connection layercomprising a plurality of depressions, wherein the connection layer isdisposed between the semiconductor chip and the carrier, and wherein thedepressions or part of them have a depth so that they do not reach themain face of the semiconductor chip; and a filler material disposed inthe depressions of the connection layer.
 2. The electronic componentaccording to claim 1, wherein the filler material comprises aheat-shrinkable material.
 3. The electronic component according to claim1, wherein the filler material comprises an adhesive material.
 4. Theelectronic component according to claim 1, wherein the filler materialcomprises a host material filled with conductive particles.
 5. Theelectronic component according to claim 1, wherein the semiconductorchip comprises an electrical device having a first electrical contactelement at the main face and a second contact element at a further mainface opposite to the main face.
 6. The electronic component according toclaim 5, wherein the electrical device comprises a vertical transistor,an MOS transistor, an IGB transistor, or a power transistor.
 7. Theelectronic component according to claim 5, further comprising anelectrically conductive layer disposed onto the first electrical contactelement, wherein the depressions are formed into the electricalconductive layer.
 8. The electrical component according to claim 1,wherein the semiconductor chip further comprises a further main faceopposite to the main face, the electrical component further comprising afurther connection layer disposed on the further main face of thesemiconductor chip, the further connection layer comprising a pluralityof depressions.
 9. The electronic component according to claim 1,wherein the depressions are formed as columns, the columns havingvertical side faces.
 10. The electronic component according to claim 1,wherein the depressions have one or more of equal form, equal dimensionsand equal distances from each other.
 11. The electronic componentaccording to claim 1, wherein the depressions are arranged in a regularmanner.
 12. The electronic component according to claim 1, wherein thefiller material is an electronically conductive material.